[PATCH printk v2 25/26] rcu: Mark emergency section in rcu stalls

[John Ogness <john.ogness@linutronix.de>]

Mark an emergency section within print_other_cpu_stall(), where
RCU stall information is printed. In this section, the CPU will
not perform console output for the printk() calls. Instead, a
flushing of the console output is triggered when exiting the
emergency section.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 kernel/rcu/tree_stall.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ac8e86babe44..efb2be8939a2 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -9,6 +9,7 @@
 
 #include <linux/kvm_para.h>
 #include <linux/rcu_notifier.h>
+#include <linux/console.h>
 
 //////////////////////////////////////////////////////////////////////////////
 //
@@ -604,6 +605,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 	if (rcu_stall_is_suppressed())
 		return;
 
+	nbcon_cpu_emergency_enter();
+
 	/*
 	 * OK, time to rat on our buddy...
 	 * See Documentation/RCU/stallwarn.rst for info on how to debug
@@ -658,6 +661,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
 	panic_on_rcu_stall();
 
 	rcu_force_quiescent_state();  /* Kick them all. */
+
+	nbcon_cpu_emergency_exit();
 }
 
 static void print_cpu_stall(unsigned long gps)
-- 
2.39.2